FIELD OF INVENTION
The present invention relates to electrical temperature sensing devices and more particularly to a remote temperature warning system for a refrigeration vehicle which utilizes the existing wiring of the vehicle. 2. Description of Prior Art
An indispensible requirement for transporting perishable food items, or the like, is a carefully controlled temperature environment. Refrigerated transportation vehicles such as a refrigeration truck provided such a controlled environment, but only to the extent that the temperature control system of the vehicle is operating properly. It all too often happens, with substantial monetary losses, that a refrigeration vehicle operator will operate his vehicle for a considerable length of time totally unaware that a malfunction in the temperature control system has occurred.
Present temperature control systems have temperature indicating means affixed directly to the refrigeration compartment of the vehicle in direct connection with the temperature sensors inside the compartment. Such a device is disclosed in U.S. Pat. No. 3,594,752 to Alton. Alton includes a temperature sensitive thermistor electrically connected to an externally disposed alarm unit through a hole drilled in the refrigeration vehicle wall to which the device is mounted. The mounting of such a device thus requires modification to the compartment wall and contemplates that the thermistor element be disposed proximate the alarm unit.
It is advantageous, however, to provide a temperature change warning system wherein the temperature indication means can be remotely placed from the temperature sensing device and be installed without having to substantially rewire or otherwise modify the vehicle. It is further advantageous to provide such an easily installed device having a remote preferrably visual temperature indication means installed within the cab of the vehicle for continued monitoring while the vehicle is being operated, as well as an audio alarm on the refrigeration compartment for warning of a temperature control system malfunction when the vehicle is not being operated and the driver is outside the cab.
The present invention is a temperature change warning device which provides remote temperature sensing with high reliability and which can be easily installed on a vehicle having an existing refrigeration control unit with minimal wiring and minimum modification to that vehicle.